Problem with my nano lights

[Octupus]

hi.. i purcahsed a used 15 gallon nano tank. The lights are being flaky and i am not sure if it is the bulbs or the circuit/connection. if i hold/push at the socket the lights turn but few seconds later they go off again. the fan is working but not hte lights. Any suggestions? if it is the bulb, any suggestion where to buy the bulb and how much roughly? Thank you!